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Good Morning All!,
After a significant amount of reading and tinkering, I'm stumped. We have a pair of Arctic Cat DVX 90s (4-stroke), and one of them runs very rich at wide open throttle. I've cleaned the carb (which was installed new last year), verified the main jet (80) to be per the original spec, installed a new air filter, tried a hotter spark plug (CR6HSA), and adjusted the valves (tightened a modest 0.0005" but improved starting). The hotter spark plug may have help just a bit, but not appreciably.
Just for fun, I swapped the CDI between machines, and that didn't help either.
Fouling plugs very quickly, but not to the point the machine will not run or start. [black instantly]
Logically, I assume I'm revving out, but the other machine doesn't "stumble/blubber" anything like this one.
Should I try a smaller main jet?
Any ideas you guys may have would be much appreciated.
Thanks in advance everyone.
By matthew smith
I have a honda recon 250 that i just bought. the compression is around 90 needs to be rebuilt. im getting into rebuilding it took apart the top end no problem except for the cylinder walls. as shown in the pictures. the way the piston sits in the cylinder is if you were sitting on the wheeler the skirt on the piston is left to right. so the wrist pin is front to back. which is where the two marks are in the cylinder. so that means the connecting rod is making the piston slap the cylinder on the wrist pin side which seems like a weird way for the cylinder to be moving. not natural. now the connecting rod has slight play left to right but not up and down. ive talked to a few people they say it might be the roller bearings in the connecting rod where it meets the crankshaft. but the play it has is not that much. im just looking for some more input before i start splitting the case.
By Justice Owens
Hey guys, any ideas would be greatly appreciated on this.
So it started a few months ago, riding with some buddies and my 400ex all of a sudden lost power. Wouldn't fire, wouldn't sputter. Towed it home, and then it fired right up. It continued this pattern for a week or two, ran perfectly for varying amounts of time, suddenly died, and would start right back up if I waited 20 mins or so.
Now we get to the next phase... I was dinking with it one day, I think I pulled the carb off and cleaned it out, (not really dirty but just to be sure) and I was trying different fuel screw adjustments. At any rate, I didn't notice much change, except obviously running a little poorer when I had the fuel screw in the wrong place. I took it on a quick ride around the block, and it was just fine. Ran awesome, had lots of power, etc. Then went around the block again and it died on me this time right as I revved it. Ever since then I haven't been able to get it to start.
Now when I turn it over, it sputters, fires a touch, but won't start. Ever. I replaced the plug, CDI, and coil, with no change. I do know that it has spark, but I don't know for certain that its big enough. After replacing these with no change I popped the carb off and tried firing it up spraying some either right into the intake. Upon doing so, it revved right up, but obviously there was no carb so it didn't stay running for long. While spraying the ether it seemed to run just like other engines I've tried spraying ether into no popping or backfiring etc. When it fired right up on the ether, I figured I must have a carb issue, so I just bought a whole new carb instead of taking the old one apart for the 800th time. When I put it in, there was no change whatsoever. Still turns over and sputters, but won't fire up.
I am completely befused, and any input would be graciously accepted. If you read through all that your a trooper, so thanks very much :)
By Dra O
posted a while back - it was running at one point - I have all the plastic shroud off - it's down to frame and engine now
-fuel pump: when line from petcock is attached, no fuel comes out other side to carb; the line to the carb is open (can blow through it); I thought when I cranked engine that the pump would spit out fuel on other side but it does not; I removed fuel pump and opened it up - diaphragm looks good - but internal areas had lotsa calcification build up - I cleaned this out and dried it good - the clear plastic pieces (?diaphragms) aren't broken - the spring w/ steel ball on end moves freely; am putting it back on tomorrow; but can anyone answer about the pump? isn't it supposed to pump fuel through it... to other side... to carb? puzzling
-along with fuel pump: I replaced petcock 3 weeks ago (gas tank had rusty fuel in bottom - cleaned it out prior to new petcock); when I turn petcock arrow NOT to on or reserve, fuel comes out of line; when I turn it to on or reserve, fuel doesn't come out; puzzling
-I don't know what's on back of fuel pump - it's a valve that has a hose coming out of it - looks like it goes to engine/carb - I haven't traced this out yet - what is it?
-can squirt gas on air filter and engine will run for 2-3 seconds then stop - fuel in top of carb (under diaphragm) does same
-it likely needs carb rebuild - will get to this - but something isn't allowing fuel to get from fuel pump to carb
-I THINK it has a mikuni model x carb - diaphragm is ID 26mm OD 68mm - hard to find inexpensive diaphragm, I guess because it's a model x
-last thing - I replaced solenoid due to old one clicking; I HAVE to be charging the battery or it won't start/turn over - battery just goes dead; but if charging, it'll turn over nicely; i'm guessing it's a bad battery
-any help appreciated - I've never owned an ATV before - inherited this beast from grandparent in-law
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